The only "fix" I found for this was to disable LTE. The problem seems to be with the device switching between LTE and 3G. Many times the transition is not smooth or does not happen at all. Since 3G is available all over, switching LTE off will force the device to stay on 3G and never try to look for or transition to the LTE network. The only down side is you lose network speed, but you can always switch LTE back on when you need the speed and shut it right back off again to avoid the network transition problem. In any event, this is only a work around and this problem is a BIG bug.